For the purpose of a higher charge readout speed in a solid-state image pickup device, a solid-state image pickup device having a potential gradient structure formed by dividing a diffusion layer of a photodiode into a plurality of regions and changing the impurity concentrations of the regions is known (for example, refer to Patent Document 1). Further, for the same purpose, a solid-state image pickup device in which a charge transfer electrode is provided as an upper layer of a photodiode, and a potential gradient is formed by applying a higher voltage to the charge readout side of this electrode, is known (for example, refer to Patent Document 2).
Further, for the purpose of control of a charge accumulation time in a photodiode, a solid-state image pickup device having a charge sweep-away gate and a charge sweep-away drain region for sweeping-away unnecessary charges which are formed along an alignment direction of a plurality of photodiodes is known (for example, refer to Patent Document 3).    Patent Document 1: Japanese Published Unexamined Patent Application No. 2002-231926    Patent Document 2: Japanese Published Unexamined Patent Application No. 2005-268564    Patent Document 3: Japanese Published Unexamined Patent Application No. 2002-135660